<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        ul {
            list-style: none;
            padding: 0;
            margin: 0;
        }

        body {
            background: #23384e;
            font: 12px/1.5 \5fae\8f6f\96c5\9ed1;
        }

        .search,
        .search .inner-box,
        .search .box,
        .search .select,
        .search a {
            background: url(../images/search.jpg) no-repeat;
        }

        .search,
        .search .box,
        .search .inner-box {
            height: 34px;
        }

        .search {
            position: relative;
            width: 350px;
            margin: 10px auto;
        }

        .search .box {
            background-position: right 0;
        }

        .search .inner-box {
            background-repeat: repeat-x;
            background-position: 0 -34px;
            margin: 0 20px 0 40px;
        }

        .search .select {
            float: left;
            color: #fff;
            width: 190px;
            height: 22px;
            border: none;
            cursor: pointer;
            margin-top: 4px;
            line-height: 22px;
            padding-left: 10px;
            background-position: 0 -68px;
        }

        .search a {
            float: left;
            width: 80px;
            height: 24px;
            color: #333;
            letter-spacing: 4px;
            line-height: 22px;
            text-align: center;
            text-decoration: none;
            background-position: 0 -90px;
            margin: 4px 0 0 10px;
        }

        .search a:hover {
            color: #f60;
            background-position: -80px -90px;
        }

        .search ul {
            position: absolute;
            top: 26px;
            left: 40px;
            color: #fff;
            width: 198px;
            background: #2b2b2b;
            border: 1px solid #fff;
            display: none;
        }

        .search ul li {
            height: 25px;
            line-height: 24px;
            cursor: pointer;
            padding-left: 10px;
            margin-bottom: -1px;
            border-bottom: 1px dotted #fff;
        }

        .search ul li:hover,
        .search ul li.active {
            background: #8b8b8b;
        }
    </style>
</head>

<body>
    <div class="search">
        <div class="box">
            <div class="inner-box">
                <input type="text" id="keyword" class="select" autocomplete="off" placeholder="请选择游戏名称">
                <a href="#">搜索</a>
            </div>
        </div>
        <ul class="list">
            <li>地下城与勇士</li>
            <li>魔兽世界（国服）</li>
            <li>魔兽世界（台服）</li>
            <li>热血江湖</li>
            <li>大话西游II</li>
            <li>QQ幻想世界</li>
        </ul>
    </div>

    <script>
        /*
            实现的功能：
                【1】搜索框获取焦点的时候 显示下拉下单
                    【1】获取元素
                【2】搜索框失去焦点时候 隐藏下拉菜单

                一下两个功能只有在获取焦点的时候才会有用
                【3】按下鼠标的上下键 可以动态选中 li元素（给li元素添加 active 这个class名）
                【4】当按下 enter键的时候，把拥有 activeclass名的元素的内容 赋值给搜索框
         */

        let select = document.querySelector(".select");
        let list = document.querySelector(".list");
        let li = document.querySelectorAll("li")
        let a = 0;
        select.onfocus = () => {
            list.style.display = "block";
            let arr = []
            document.onkeydown = function (e) {
                if (e.keyCode == 38) {
                    // 上
                    li.forEach((item, index) => {
                        item.classList.remove("active")
                    })
                    if (a < 0) {
                        a = li.length - 1;
                    }
                    a--;
                    if (a < 0) {
                        a = li.length - 1;
                    }
                    li[a].classList.add("active")
                } else if (e.keyCode == 40) {
                    // 下
                    li.forEach((item, index) => {
                        item.classList.remove("active")
                    })
                    a++;
                    if (a >= li.length) {
                        a = 0;
                    }
                    li[a].classList.add("active")
                }  // } else if (e.keyCode == 37) {
                //     // 左
                // } else if (e.keyCode == 39) {
                //     // 右
                // }

                if (e.keyCode == 13) {
                    let a = document.querySelector(".active");
                    // console.log(a.innerHTML)
                    select.value = a.innerHTML
                    list.style.display = "none";
                    select.blur();
                }

            }

        }

        select.onblur = () => {
            list.style.display = "none"
        }


    </script>
</body>

</html>